Floor-engaging members for articles of furniture and the like



June 1, 1965 H. M. KESTERTON 3,186,025

. FLOOR-ENGAGING MEMBERS FOR ARTICLES OF FURNITURE AND THE LIKE Filed Oct. 10, 1962 mvzu r0 4.

Weary Ham/u 1257:1701! United States Patent 3,186,025 FLOOR-ENGAGING MEMBERS FUR ARTICLES 019 FURNITURE AND THE LIKE Henry M. Kesterton, Wroxall, England, assignor to Howard Clayton-Wright Limited, Warwick, England, a British company Filed Oct. 10, 1962, Ser. No. 229,599 Claims priority, application Great Britain, Oct. 19, 1961, 37,452/61 7 Claims. (Cl. 16-18) This invention relates to floor-engaging members of the castor type for use on articles of furniture, particularly chairs and settees, and the expression floor or floorengaging as used herein, is intended to be taken in the generic sense as referring to any surface upon which an article of furniture may be resting, although the invention is particularly concerned with the provision of a floor-engaging member of this type for use with chairs or settees which may be resting upon carpets and which need to be moved from time-to-time.

The conventional form of furniture castor generally comprises a wheel or roller carried at the lower end of a swivel pin and in the case of a wheel having a plain journal bearing, the wheel is generally of small size and has the disadvantage that the weight of the chair or settee or other article of furniture, causes the wheel to dig in and make an impression in the floor covering and this is particularly noticeable with carpets where such impressions can have a permanent damaging'eifect.

To avoid the damaging efiect of small wheels, rollers of larger diameter have been used, such rollers being rotatable about axes inclined to the horizontal but hitherto these have been of a rather bulkycharacter which detracts from the general outward appearance of the chair or settee and also have the disadvantage that any slight force is sufficient to cause movement of the article of furniture with the result that a person sitting down is liable to displace a chair or settee.

Also in these hitherto known types of. casters, each castor assembly includes two axes of rotation, one having the upright or vertical swivelling axis and the other having an inclined or horizontal axis of rotation.

The object of the invention is to provide a new or improved form of floor-engaging member of the castor type which is of simpler construction and free from the disadvantages attaching to castors used hitherto and which will also provide a true castor action without any possibility of damage to the floor covering either when at rest or when moving.

According to the invention there is provided a floorengaging member of the castor type comprising a castor body and a swivel pin which engages with the article of furniture and with the castor body in such manner as to permit of swivelling motion of the castor body about a vertical axis relative to the article of furniture, the castor body having an underneath surface, which makes contact with the fioor and which is of convex, or substantially convex form and in plan view covers a projected area which has a central axis offset from the axis of swivelling of the castor body so that the castor body engages the floor over a substantially circular zone within said projected area and eccentric in relation to the swivelling axis, and the underneath surface of the castor body being shaped so that it rises upwardly from said circular zone of engagement at a progressively increasing angle of inclination to the horizontal.

The invention is illustrated in the accompanying drawings wherein:

FIGURE 1 is a part-sectional side elevation of a castor showing one form of attachment to an article of furniture.

Patented June 1, 1965 ice FIGURE 2 is a vertical section in side elevation on the centre line of the castor and showing another form of attachment to an article of furniture. I

FIGURE 3 is an elevation in section on the centre line of the cover member of the castor, and

FIGURE 4 is an elevation in section on the centre line of the base member of the castor.

The castor shown in the attached drawings is particularly suitable for attaching to the legs of chairs or settees which are to be movable across a carpeted floor surface and in FIGURE 1 the part 10 indicates the lower end of a chair or settee leg to which the castor is fitted.

The castor body may be made in one piece but as shown in this example it comprises two parts, namelya base member 11 and a cover member 12 fitting on the base member together with a swivel pin -13 which defines the vertical or substantially vertical axis about which the castor rotates.

Although the parts 11 and 12 of the castor may be made of any suitable material, it is advantageous to make them as mouldings in a suitable plastics material, such as that known under the registered trademark Delrin which plastics material can be obtained in self-colour and several other colours so that the colour of the body of the castor can be chosen to suit or match the colouring of the article of furniture and also different colours may be chosen for the base member 11 and the cover member 12.

In the form shown in FIGURE 1, the chair leg 10 is provided with an axial upwardly extending hole 14 in which is fitted a sleeve 15 having at its lower end a circular flange 16 and screws such as 17 may be passed through suitable holes in this flange to secure the sleeve 15in position.

The sleeve 15 has an axial hole extending inwardly from its flanged end and this hole receives rotatably the upper portion of the swivel pin 13. The lower portion of the pin 13 is received rotatably in a substantially vertical and axial hole extending downwardly in an upstanding pillar 18 which is formed integrally with the base member 11 as is decribed more specifically hereinafter.

Near each end the swivel pin 13 has a circumferential groove 19 in which is fitted a circlip or split ring 20 and these two members serve to retain the swivel pin 13 within the sleeve 15 and also to retain the castor body upon the lower end of the swivel pin 13 as the split rings or circlips 20 exert sufiicient frictional resistance against the internal Wall of the holes in which they are applied to prevent displacement of the swivel pin out of the hole except, forcibly, whilst at the same time permitting the sufiiciently free relative rotation between the swivel pin 13 and the sleeve 15 and base member 11 necessary to provide the castoring action.

In the form shown in FIGURE 1 the pin 13 has pl-ain ends and may economically be produced from elongated stock by parting off at spaced positions to provide the desired lengths of pins and to provide good bearing surfaces for the ends of the pin with minimum frictional resistance to rotation, the inner end of the hole in the sleeve 15 and the base of the hole in the pillar 18 are formed with a projecting convex or part-spherical surface 21. As the sleeve 15 as well as the parts 11 and 12 of the castor body may also be conveniently be produced as mouldings in suitable plastics material, the provision of the projecting such as where the chair is one which has outwardly splayed legs instead of vertically extending legs.

In this case there is provided a metal attachment plate 22 which can be secured to the lower end surface of the leg by any suitable means and in this case the swivel pin 23 has an externally projecting flange 24 near its upper end and this end, which projects from the top face of the castor body is secured in a hole formed in a pressed out portion 25 of the plate 22 by peening over or otherwise deforming the upper end of the pin 23 to provide the head 26 which thus fixes the upper end of the pin in the plate 22.

The lower end of the pin 23 is rotatably received in the axial hole in the pillar 18 in the same manner as shown in FIGURE 1.

Referring now to FIGURES 3 and 4 which show the cover member and base member respectively in the separated state, the base member 11 has its contact surface formed as a sole plate and in plan view the part 27 of the base member is circular and the sole plate is of generally convex form over its major portion. This contact surface comprises a major portion extending over the area defined between the points 28 and of spherical configuration with a radius of curvature lying upon the line 29 so that on a tangential surface as indicated by the line 30, the convex surface 2828 would make substantially point contact at the position 31 which lies on the radial axis 29 of the convex surface, this radial axis being offset by the distance (D) from the axis 32 of the axial hole 33 in which is rotatably seated the .lower end of the swivel pin, the axis 32 therefore being the axis of the swivel pin and the axis about which the castor body rotates. The axis 32 intersects an element of the contact surface spaced from the position 31 at an oblique angle.

It will be observed that the remainder of the surface of the base member 11 comprises the curved edge surface extending between the positions 28 and the position 34 and this surface is defined by curvature of considerably smaller radius than that of the convex surface 2828 so that the aforesaid surface between the positions 28 and 34 extends upwardly at a substantially steeper angle than the angle defined between the convex surface 28 and the floor plane 30.

It will be appreciated of course that in practice the base member 11 does not make point contact with the surface upon which it is resting but makes contact over a circular zone having its centre at the point 31. When used with a carpet having a pile which is the main intended use of such a castor, the engagement between the sole plate of the base member 11 and the carpet will be over a fairly substantial zone of the convex surface 28-28, this zone being circular and having its centre at the point 31 and in fact the castor will create a concave of saucershaped depression in the pile of the carpet.

Because of the convex form of the under-surface or sole plate of the base member 11, a force applied in any direction to the castor will tend to cause the convex surface to ride up out of the depression created in the carpet and this action is further assisted by the provision of the more steeply inclined annular edge surface between the positions 28 and 34 on the underface of the base member. Also this particular formation of the under-surface ensures a varying degree of pressure on the carpet the maximum pressure being over the central zone around the centre point 31 and gradually reducing at positions outwardly of this zone.

Therefore the castor has the advantage that even though depressions are created in the carpet due to the Weight of the chair or settee, such depressions will not interfere with the true castoring action when a force is applied to move the article of furniture because irrespective of the relative positions of the castors, the force applied will act upon each castor so as to immediately cause the base member to tend to ride up out of the depression in the carpet and tend to turn the castor into its true trailing position for proper castoring action.

Due to the eccentric relationship between the axis 32 of the swivel pin and the axis 29 of the circular zone of engagement between the base member and the carpet, initial ulling or pushing of the article of furniture will at once result in relative movements to bring the castor body into true trailing relationship with the swivel pin 13 so that thereafter an easy sliding motion can be obtained with true castor action.

It will also be observed that the axial hole 33 in the pillar 18 extends down to a position close to the undersu-rface of the base member 11 so as to provide for the transmission of a dragging force applied through the swivel pin at a position which is close to the under-surface of the base member 11 so that there is little or no tendency for the base member to tilt relative to the axis.

Also this feature enables sufiicient bearing support for the spindle to be obtained within the body of the castor so that the overall height of the castor can be reduced and also the arrangement of FIGURE 2 can be used where desired in which all the rotational movement of the pin takes place within the body of the castor, the upper end of the pin being fixed to the lower end of the peg of the chair or settee.

On the upper part 27 of the base member there is provided a platform 35 of circular form in plan view except for the provision of a radially extending slot 36 and the peripheral edge of this platform 35 is provided with a projecting rib 37 having outwardly converging side faces 38.

The cover member 12 shown in FIGURE 3 is of generally hollow form provided at its upper end with a circular opening 39 which is adapted to seat about the reduced shoulder portion 40 at the upper end of the pillar 18 and on its inner surface the cover member 12 has a peripherally extending groove 41 of a form complementary to the rib 37 on the platform 35. The groove 41 is continuous around the periphery except for interruption by a web 42 extending radially inwards of the cover member which web 42 is adapted to engage in the radial slot 36 in the platform 35 when the cover member is placed in position and with the formation of the parts in a suitable plastics material having inherent resiliency, the cover member can be snapped into position so as to engage the groove 41 over the projecting rib 37 and locate the two parts together by means of the engagement between the web 42 and the radial slot 36.

What I claim then is:

1. A floor engaging member of the castor type comprising, in combination:

(a) a castor body having a contact face for engagement with a floor, and a top face opposite said contact face; and

(b) swivel means on said castor body and projecting from said top face for rotatably connecting said castor body to an article of furniture,

(1) said swivel means including means defining an axis of relative rotation of said castor body and of a connected piece of furniture,

(2) said axis defining means including bearing means fixed on said castor body and said swivel means further including a swivel pin projecting from said top face, said pin being received in said bearing means for rotation about said axis,

(3) said axis intersecting an element of said contact face at an oblique angle and being fixed with respect to said contact face element,

('4) a plane at right angles to said axis being tangential with respect to another element of said contact face radially spaced from said axis, and

(5) said contact face being of convex arcuate cross section in all planes perpendicular to said tangential plane in said other face element.

2. A floor engaging member of the castor type comprising, in combination:

(a) a castor body having a contact face for engagement with a floor, and a top face opposite said contact face; and

(b) swivel means on said castor body and projecting from said top face for rotatably connecting said castor body to an article of furniture,

(1) said swivel means including means defining an axis of relative rotation of said castor body and of a connected piece of furniture,

(2) said axis defining means including bearing means fixed on said castor body and said swivel means further including a swivel pin projecting from said top face, said pin being received in said bearing means for rotation about said axis,

-(3) said axis intersecting an element of said contact face at an oblique angle and being fixed with respect to said contact face element,

( 4) a plane at right angles to said axis being tangential with respect to another element of said contact face radially spaced from said axis,

('5) said cont-act face being of convex arcuate cross section in all planes perpendicular to said tangential plane in said other face element, and,

wherein the castor body is of circular form when viewed in the direction of said axis and comprises a base member carrying said contact face and a cover member carrying said top face, the base member having an upstanding pillar the axis of which is eccentric in relation tothe circular form of the castor body, said pillar havingan axial hole constituting said bearing means.

3. A floor-engaging member according to claim 2 wherein the base member is provided with an upstanding platform surrounding the said pillar and the cover member is of domed shape having a lower peripheral edge engaging the periphery of the platform and having an opening in the top engaging a shoulder at the upper end of the pillar.

4. A floor-engaging member according to claim 2 wherein the swivel pin is provided near its lower end with a circumferential groove and a ring member received in said groove.

5. A floor-engaging member according to claim 2 wherein the base of the axial hole in the pillar is provided with an upwardly projecting surface of domed formation and the pin has a plain lower end which rotatably seats upon said surface.

6. A floor-engaging member according to claim 2 wherein the pivot means include an attachment plate adapted to be secured to the lower end of the leg of an article of furniture, the projecting portion of said pin being fixedly attached to said plate.

7. A floor-engaging member according to claim 2, further comprising a sleeve member, the projecting part of the pin being slidably received in an axial hole of the sleeve member, said sleeve member being adapted to be fitted to the lower end of the leg of an article of furniture.

References Cited by the Examiner UNITED STATES PATENTS 1,421,647 7/22 Wolf 16--18 2,717,410 9/55 Holloman l6 42 FOREIGN PATENTS 278,881 2/52 Switzerland.

DONLEY J. STOCKING, Primary Examiner. 

1. A FLOOR ENGAGING MEMBER OF THE CASTOR TYPE COMPRISING, IN COMBINATION: (A) A CASTOR BODY HAVING A CONTACT FACE FOR ENGAGEMENT WITH A FLOOR, AND A TOP FACE OPPOSITE SAID CONTACT FACE; AND (B) SWIVEL MEANS ON SAID CASTOR BODY AND PROJECTING FROM SAID TOP FACE FOR ROTATABLY CONNECTING SAID CASTOR BODY TO AN ARTICLE OF FURNITURE, (1) SAID SWIVEL MEANS INCLUDING MEANS DEFINING AN AXIS OF RELATIVE ROTATION OF SAID CASTOR BODY AND OF A CONNECTED PIECE OF FURNITURE, (2) SAID AXIS DEFINING MEANS INCLUDING BEARING MEANS FIXED ON SAID CASTOR BODY AND SAID SWIVEL MEANS FURTHER INCLUDING A SWIVEL PIN PROJECTING FROM SAID TOP FACE, SAID PIN BEING RECEIVED IN SAID BEARING MEANS FOR ROTATION ABOUT SAID AXIS, (3) SAID AXIS INTERSECTING AN ELEMENT OF SAID CONTACT FACE AT AN OBLIQUE ANGLE AND BEING FIXED WITH RESPECT TO SAID CONTACT FACE ELEMENT, (4) A PLANE AT RIGHT ANGLES TO SAID AXIS BEING TANGENTIAL WITH RESPECT TO ANOTHER ELEMENT OF SAID CONTACT FACE RADIALLY SPACED FROM SAID AXIS, AND (5) SAID CONTACT FACE BEING OF CONVEX ARCUATE CROSS SECTION IN ALL PLANES PERPENDICULAR TO SAID TANGENTIAL PLANE IN SAID OTHER FACE ELEMENT. 